SATA (Serial ATA) Interface Overview for SSD (Solid State Drives) and Modules

SATA is a computer bus specifically for connecting mass storage devices to host systems. SATA stands for Serial ATA and is the follow-on interface to the PATA (Parallel ATA) interface originally designed in 1986.

The Serial ATA (SATA) interface was created in 2003 by the Serial ATA Working Group, which was later incorporated as a non-profit named the Serial ATA International Organization (SATA-IO).

The SATA interface was designed to be a much faster interface than PATA. Higher SATA speeds were arrived at by a much increased data rate on serial paired lines for transmit and receive.

The ATA/ATAPI basic interface commands used for the earlier PATA interface are supported by SATA to make the command set backward compatible.

A Brief History of the SATA Interface Revisions

SATA VersionMaximum PerformanceHighlighted Features
Revision 1.0
1.5 Gbits/sec
(150 MBytes/sec)
Initial SATA Launch
Revision 2.0
3.0 Gbits/sec
(300 MBytes/sec)
Backward Compatible with SATA 1.5 Gbits/sec
Revisions 2.5/2.6
3.0 Gbits/sec
(300 MBytes/sec)
NCQ (Native Command Queuing
Slimline/Micro Cables & Connectors
Revision 3.0
6.0 Gbits/sec
(600 MBytes/sec)
Backward Compatible with SATA 3.0 Gbits/sec
Revision 3.1
6.0 Gbits/sec
(600 MBytes/sec)
mSATA (MO-300) Defined
TRIM Command
Revision 3.2
16 Gbits/sec
(1969 MBytes/sec)
m.2 (NGFF) Defined
SATA Express Spec

2.5" SATA SSD and Slim SATA (MO-297) Connector

The standard SATA connector found on 2.5” SATA SSD and Slim SATA (MO-297) are the same as shown above. There are a total of 22-pins broken into 7-pins for Data and 15-pins for Power.

The contact pads for these products is only found on one side of the connector. As you can see by the image, some pads are longer so they will make contact sooner when the connector is inserted. This is done to make sure the devices start up properly when hot swapping.

The detailed signal breakdown as used on the Cactus Industrial Grade SATA SSD are shown in the table below.

Pin NumberAssignmentDescription
S1 - DataGroundFirst to Contact
S2 - DataA+Host (Transmit +)
S3 - DataA-Host (Transmit -)
S4 - DataGroundFirst to Contact
S5 - DataB-Host (Receive -)
S6 - DataB+Host (Receive +)
S7 - DataGroundFirst to Contact
Coding Notch Keys the Connector
P1 - Power+3.3 V3.3 V Source
P2 - Power+3.3 V3.3 V Source
P3 - Power+3.3 V3.3 V Source
P4 - PowerGroundFirst to Contact
P5 - PowerGroundFirst to Contact
P6 - PowerGroundFirst to Contact
P7 - Power+5.0 V5.0 V Supply
P8 - Power+5.0 V5.0 V Source
P9 - Power+5.0 V5.0 V Source
P10 - PowerGroundFirst to Contact
P11 - PowerActive LEDActivity LED
P12 - PowerGroundFirst to Contact
P13 - Power+12.0 V12.0 V Source
P14 - Power+12.0 V12.0 V Source
P15 - Power+12.0 V12.0 V Source

mSATA (MO-300) Connector

The mSATA (MO-300) uses a slightly different connector than the 2.5” and Slim SATA. There are a total of 52-pins, with 26-pins on each side of the circuit board.

Below is a detailed signal breakdown as used on the Cactus Industrial Grade mSATA SSD.

Pin #AssignmentDescriptionPin #AssignmentDescription
1N/AN/A27GroundReturn Current Path
2+3.3 V3.3 V Source28N/AN/A
3N/AN/A29GroundReturn Current Path
4GroundReturn Current Path30N/AN/A
5N/AN/A31Rx-SATA Differential
7N/AN/A33Rx+SATA Differential
8N/AN/A34GroundReturn Current Path
9GroundReturn Current Path35GroundReturn Current Path
10N/AN/A36ReservedNo Connect
11N/AN/A37GroundReturn Current Path
12N/AN/A38ReservedNo Connect
13N/AN/A39+3.3 V3.3 V Source
14N/AN/A40GroundReturn Current Path
15GroundReturn Current Path41+3.3 V3.3 V Source
17N/AN/A43GroundReturn Current Path
18GroundReturn Current Path44N/AN/A
21GroundReturn Current Path47ReservedN/A
23Tx+SATA Differential49DA/DSSDevice Activity/Disable Staggered Spin Up
24+3.3 V3.3 V Source50GroundReturn Current Path
25Tx-SATA Differential51Presence DetectionPulled to Ground by Device
26GroundReturn Current Path52+3.3 V3.3 V Source

Other SATA Modules

To round out the Cactus SATA interface offering, we have CFast products which are defined by the CompactFlash Association and possibly a future M.2 (NGFF) form factor.

Cactus offers both an Industrial Grade CFast and MLC CFast card to meet different OEM market requirements. I will provide more details on these parts in another post.

As always, if you need more information on the Cactus products to assist with a design, Talk to a Cactus Expert.

Steve Larrivee has over 30 year's experience in the data storage market, including 5 years at Seagate Technology and 10 years at SanDisk. He joined Cactus Technologies Limited as an equity partner and Co-Founded Cactus USA in 2007 with partner Tom Aguillon. Learn more about Steve on Google+